Conventional cardboard boxes used to transport objects are frequently subjected to considerable stress, depending on what is transported in the box. If books or phonograph records are transported, for example, weights on the order of 400 to 500 pounds must be carried in a box with a volume of about 40 liters. These stresses do not affect the material of the box uniformly, rather, certain areas of the box experience substantial peak loads.
A prior art box is disclosed in U.S. Pat. No. 3,178,093 to Wasyluka, but it is not suitable for transporting relatively heavy objects. In another prior art box disclosed in U.S. Pat. No. 4,037,777 to Maughan, end walls of the box are each joined to an extension attached by a folding line. An inner, partially stamped portion of the extension, which in turn includes a partially stamped tab, reinforces the gripping hole of the box, but provides only a slight improvement in the properties of the box.